Holding a cell phone to the ear for an extended period of time increases activity in regions of the brain closest to the antenna, researchers have found.

Action Points

Note that in this study, in healthy participants and compared with no exposure, 50-minute cell phone exposure was associated with increased brain glucose metabolism in the regions closest to the antenna.

Point out, however, that the physiologic or clinical significance of these findings as well as the cause is unclear and it is not known if there are any harmful or long-term consequences.

Holding a cell phone to the ear for an extended period of time increases activity in regions of the brain closest to the antenna, researchers have found.

Glucose metabolism in the orbitofrontal cortex and temporal pole increased significantly when the phone was turned on and muted, compared with when it was off (P=0.004), Nora Volkow, MD, director of the National Institute on Drug Abuse, and colleagues reported in the Feb. 23 issue of the Journal of the American Medical Association.

"Although we cannot determine the clinical significance, our results give evidence that the human brain is sensitive to the effects of radiofrequency-electromagnetic fields from acute cell phone exposures," co-author Gene-Jack Wang, MD, of Brookhaven National Laboratory in Long Island, where the study was conducted, told MedPage Today.

Although the study can't speak to what the long-term implications might be, other researchers are calling the findings significant.

"Clearly there is an acute effect, and the important question is whether this acute effect is associated with events that may be damaging to the brain or predispose to the development of future problems such as cancer as suggested by recent epidemiological studies," Santosh Kesari, MD, PhD, director of neuro-oncology at the University of California San Diego, said in an e-mail to MedPage Today and ABC News.

There have been numerous epidemiological studies evaluating the potential links between brain cancer and cellphone use, and the results have often been inconsistent or inconclusive.

Most recently, the anticipated Interphone study was interpreted as "implausible" because some of its statistics revealed a significant protective effect for cell phone use -- except for the most intense users (who had an increased risk of glioma) although that level was determined to be unrealistic.

But few researchers have looked at the actual physiological effects that radiofrequency and electromagnetic fields from the devices can have on brain tissue. Some have shown that blood flow can be increased in specific brain regions during cell phone use, but there's been little work on effects on neuronal activity.

So Volkow and colleagues conducted a crossover study at Brookhaven National Laboratory, enrolling 47 patients who had one cell phone placed on each ear while they lay in a PET scanner for 50 minutes.

The researchers scanned patients' brain glucose metabolism twice -- once with the right cell phone turned on but muted, and once with both phones turned off.

There was no difference in whole-brain metabolism whether the phone was on or off.

But glucose metabolism in the regions closest to the antenna -- the orbitofrontal cortex and the temporal pole -- was significantly higher when the phone was turned on (35.7 versus 33.3 mcmol/100 g per minute, P=0.004).

Regression analyses confirmed that the regions expected to have the greatest absorption of radiofrequency and electromagnetic fields from cell phone exposure were indeed the ones that showed the larger increases in glucose metabolism.

"Even though the radio frequencies that are emitted from current cell phone technologies are very weak, they are able to activate the human brain to have an effect," Volkow said in a JAMA video report.

The effects on neuronal activity could be due to changes in neurotransmitter release, cell membrane permeability, cell excitability, or calcium efflux.

It's also been theorized that heat from cell phones can contribute to functional brain changes, but that is probably less likely to be the case, the researchers said.

Wang noted that the implications remain unclear -- "further studies are needed to assess if the effects we observed could have potential long-term consequences," he said -- but the researchers have not yet devised a follow-up study.

"The take-home message," Kesari said, "is that we still don't know, more studies are needed, and in the meantime users should try to use headsets and reduce cell phone use if at all possible. Restricting cell phone use in young children certainly is not unreasonable."

This article was developed in collaboration with ABC News.

The study was supported by the National Institutes of Health and the Department of Energy.

The researchers reported no conflicts of interest.

Reviewed by Zalman S. Agus, MD Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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